A pitot tube or probe is typically mounted on a vehicle and measures the velocity of a vehicle relative to a fluid in which the vehicle is moving. In one application, a pitot probe is mounted upon an aircraft and measures the velocity of the aircraft relative to the air mass during flight. Pitot probes generally include a hollow tube that defines an open end pointing in the direction of fluid flow or vehicle movement. The hollow tube of the pitot probe contains a fluid, such as air in the case of an aircraft. The pressure within the pitot probe provides a stagnation pressure measurement, which is also called total pressure. The total pressure is combined with a static pressure, which is typically measured at a different location on the aircraft fuselage, or on the side of the pitot probe in the case of a combined pitot-static probe, in order to determine an impact pressure. The impact pressure is used to determine the airspeed of the aircraft.
Sometimes pitot probe based airspeed systems may produce incorrect airspeed readings. The incorrect reading may be caused by issues such as probe contamination, damage to the probe, or maintenance issues. Some examples of probe contamination include, but are not limited to, ice, volcanic ash, and insect invasion. Systems that estimate airspeed based on a model of an aircraft currently exist, however these systems may not be able to calculate an accurate airspeed if the aircraft is operating at extreme flight conditions. Extreme flight conditions may include unsteady or highly dynamic conditions that are typically created as the aircraft performs a maneuver, or if the aircraft experiences significant forces due to ambient winds or turbulence. Extreme flight conditions are usually determined based on the rate of change of an angle of attack, an angle of sideslip, or a bank angle. The traditional approach is to freeze or keep the airspeed estimate constant while the aircraft operates at the extreme conditions. However, if the aircraft continues to operate during the extreme conditions for more than a few seconds, this may affect the accuracy of the airspeed readings.